Transmission of energy in high power electrical systems requires the use of high-voltage (hv) insulation in coaxial lines. For special applications, some of which may not yet be practicable at this time, nonlinear insulation may have to be employed to allow for a decrease of the rise time of electromagnetic pulses generated in the above-identified conditions. As an example, generation of picosecond time domain fields in terawatt (TW) power range may be needed to effect molecular (hot) fusion.
High voltage insulation presently used in generation and transmission of energy in high power electrical systems does not, and is not required to meet the extreme requirements of the special applications mentioned above. While it is known that for linear insulating materials, the thickness and dielectric properties of insulation determine the maximum working voltage carded by the conductor protected by such insulation, the total diameter of a coaxial line for a highly concentrated transmission of the extremely short hv energy pulses is actually limited.
R is known in the art to use multi-layer insulating structures, serving also as spacer structures, for coaxial lines. Such structure is known from U.S. Pat. No. 3,469,281 to McMahon. A number of continuous or discontinuous layers of insulating material is wrapped around an inner conductor of electrical cable. The layers are separated from each other by a plurality of radially extending ribs which are wrapped helically around the conductor in the longitudinal direction.
It is also known to fill spaces created by such interspaced layers of insulation with fluids, i.e., dielectric gases, liquids or semi-liquids.
The helical arrangement of the spacers affords flexibility to the electrical cable. In the special applications above-mentioned, however, flexibility is less important while the dielectric strength and resistance to treeing and tracking ("walking"), known phenomena leading to electric breakdown of the cable (transmission system), must be maximized.